I haven't been whale watching per se. But I took a very small boat to the Arcos off the coast of Puerto Vallarta. I went to see the blue-footed booby birds that nest on the rocks. The marine life was incredible around those rocks. Anyway, not too far from the little boat a couple of whales breached. I would say maybe a couple of hundred yards away. They were so big, if one was any closer, they would have capsized our little dingy.
During the Winter you can see whales breaching from the beach in Puerto Vallarta. No need to go out there with them. They are not that far off the shore either. A full breach is spectacular to see.